Field of the Invention
The present invention relates to a sheet feeding apparatus positioning a sheet by making a widthwise side edge of the sheet orthogonal to a sheet feeding direction abut against a reference plane and to an image forming apparatus such as a copier, a printer, a facsimile, and others including the same.
Description of the Related Art
A sheet must be supplied to an image forming portion in a condition in which position of the sheet is straightened in order to form an image on a correct position of the sheet in an image forming apparatus such as a copier, a printer, a facsimile, and others. Then, there is known a configuration of making a widthwise side edge of the sheet, on which an image is to be formed, abut against a reference plane as one of configurations of positioning the widthwise edge orthogonal to a sheet feeding direction.
For instance, Japanese Patent Application Laid-open No. Hei.06-92475 discloses a configuration of forming the reference plane against which the sheet widthwise side edge is made abut by making a reference plane provided on a side of a sheet feed cassette to be attached to the apparatus body in flush with a reference plane provided on an apparatus body side.
Specifically, according to Japanese Patent Application Laid-open No. Hei.06-92475, a reference plate within the apparatus body is provided with an inclined surface formed at a lower end portion thereof. The inclined surface is directed to a center side of the apparatus body. Still further, a reference guide formed in the sheet feed cassette on the downstream side of the sheet feed cassette is held by a holding member and includes a project portion projecting above the holding member. An inclined surface facing outside of the sheet feed cassette is formed on the project portion and the inclined surface is located at a position abuttable with an inclined surface of the reference plate of the apparatus body. The sheet feed cassette is biased to a reference plate side on the apparatus body side by a bias portion such as a side spring in a condition in which the sheet feed cassette is attached to the apparatus body. Accordingly, in response to the attachment of the sheet feed cassette to the apparatus body, the inclined surface of the reference guide of the sheet feed cassette is brought into pressure contact with, as if it is drawn into, the inclined surface of the reference plate of the apparatus body. Thereby, the reference plane of the reference guide is position to be flush with the reference plane of the reference plate.
Still as another method, according to Japanese Patent Application Laid-open No. Hei.06-92475, a positioning plate of the reference plate provided in the apparatus body is formed by bending a lower end portion of the reference plate. Still further, a groove including an opening provided in the sheet feed cassette is formed in the holding member whose upper surface is on a same level with the reference guide. This arrangement makes it possible to position the reference plane of the reference plate on the apparatus body side in flush with the reference plane of the reference guide on the sheet feed cassette side when the sheet feed cassette is attached to the apparatus body.
Conventionally, the reference plane on the apparatus body side is made in flush with the reference plane on the sheet feed cassette side by constructing as described above.
However, a downsized and quick-printing speed image forming apparatus is demanded in the recent market. In order to attain such demands, it is necessary to shorten a distance for conveying a sheet from the sheet feed cassette to the image forming portion.
If a length of the reference plate on the apparatus body side is shortened by shortening the sheet conveying distance from the sheet feed cassette to the image forming portion in the system of making the widthwise side edge of the sheet abut against the reference plate by obliquely feeding the sheet in particular, a small gap generated between the reference plane of the apparatus body and the reference plane of the sheet feed cassette may cause a negative influence on a skew correcting ability. However, in the configuration of forming the reference plane against which the widthwise side edge of the sheet abuts by making the reference plane provided in the sheet feed cassette with the reference plane provided in the apparatus body as described above, the small level difference is inherently generated due to its configuration.
That is, there is a problem that the small level difference between the reference planes of the apparatus body side and of the sheet feed cassette side degrades the skew correcting ability if the downsized and quick-printing speed image forming apparatus is to be provided.